Subject: [mobile-ip] Question on checksum for Mobility Header

From: "Krishna Kumar" <[email-masked]>
Date: Thu, 12 Sep 2002 16:31:40 -0700

Hi all,

I have a question in section 6.1.1. The Checksum field says that use
section
8.1 of IPv6 RFC to determine values for the pseudo-header. That section
says :

        The Upper-Layer Packet Length in the pseudo-header is the
         length of the upper-layer header and data (e.g., TCP header
         plus TCP data).  Some upper-layer protocols carry their own
         length information (e.g., the Length field in the UDP header);
         for such protocols, that is the length used in the pseudo-
         header.  Other protocols (such as TCP) do not carry their own
         length information, in which case the length used in the
         pseudo-header is the Payload Length from the IPv6 header, minus
         the length of any extension headers present between the IPv6
         header and the upper-layer header.

This packet is going to contain only a Mobility Header, so is the Upper
Layer Packet Length going to be zero ? The last sentence (the one about
TCP) seems to imply that, don't count the length of the extension headers
(which MH happens to be).

Any insight into this ?

Thanks,

- KK

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From: Jari Arkko <[email-masked]>
Date: Fri, 13 Sep 2002 08:03:10 +0300

> (which MH happens to be).

The intention is that MH is a final header, i.e., like TCP in this
respect. But you are right that the text doesn't explicitly say this.
I propose to add the following to 6.1.1:

   "The Mobility Header is considered as the upper layer protocol
    for the purposes of calculating the pseudo-header. The Upper-Layer
    Packet Length field in the pseudo-header MUST be set to the
    value of the Header Len field from the Mobility Header, multiplied
    by eight."

Jari

---

From: Vijay Devarapalli <[email-masked]>
Date: Tue, 24 Sep 2002 18:47:24 -0700

>     value of the Header Len field from the Mobility Header, multiplied

Please dont do this. We havent decided whether to include the 
first 8 octets of the Mobility Header in the 'Header Len' field.

I would prefer the text to say    

    "The Mobility Header is considered as the upper layer protocol
     for the purposes of calculating the pseudo-header. The Upper-Layer
     Packet Length field in the pseudo-header MUST be set to the
     the total length of the Mobility Header"

regards
Vijay

---

From: Vijay Devarapalli <[email-masked]>
Date: Tue, 24 Sep 2002 18:57:00 -0700

> first 8 octets of the Mobility Header in the 'Header Len' field.

Looks like we have decided to exclude the first 8 octest. Good.

---

From: Jari Arkko <[email-masked]>
Date: Thu, 26 Sep 2002 17:11:33 +0300

>>     the total length of the Mobility Header"

So, are you happy with the text in

http://www.piuha.net/~jarkko/publications/mipv6/issues/issue111.txt
http://www.piuha.net/~jarkko/publications/mipv6/issues/issue93.txt
http://www.piuha.net/~jarkko/publications/mipv6/issues/issue89.txt

---

From: Vijay Devarapalli <[email-masked]>
Date: Thu, 26 Sep 2002 10:13:06 -0700

> http://www.piuha.net/~jarkko/publications/mipv6/issues/issue89.txt

89 and 93 are fine. the text in issue 111 should say

"The Upper-Layer

instead of 

"The Upper-Layer

because the Header Len does not include the first 8 octets 
(issue 93).

it is minor.

Vijay